The George Washington University School of Engineering and Applied Science Department of Electrical and Computer Engineering Circuit Design Verification Using PSpice (Cadence/OrCAD) Jason Woytowich (former GTA) Farid Hassani (ECE GTA)

• Introduction • General Process Outline • Basic Example – Half-Wave Rectifier • Advanced Example – Demodulation

Introduction • SPICE is a general purpose circuit simulation language that performs non-linear DC, transient and linear steady state AC analysis.

• SPICE models: – Linear circuit elements of resistance, capacitance, inductance, independent and dependent current and voltage sources – Four of the most common nonlinear semiconductor devices (Diodes, BJTs, JFETs and MOSFETs) – Other useful circuit elements including transmission lines and mutual inductance

Cadence PSpice • OrCAD bought MicroSim and its PSpice products in January 1998.

• Cadence bought OrCAD in August 1999.

General Process 1. Design your circuit 2. Draw your circuit 3. Specify your analysis 4. Run the simulation 5. Analyze the output 6. Go back to 1, 2 or 3 as needed

Starting Cadence

Starting Cadence

Start a New Project

Select Project Options

Project Types • Only two types are of immediate concern 1. Analog or Mixed A/D The project is meant for simulation. This is for design verification.

2. Schematic This option is used for PCB design. It is only used to generate a netlist. We will use this for your Board Fabrication Details.

Create a Blank Project

Schematic

Place Parts

Placing Parts

Changing Values

Completed Half-Wave Rectifier

Create a Simulation Profile

Set the Simulation Parameters

Simulation Types • DC / OpPoint – All AC sources are zeroed (Shorted/Opened) • Transient – View with respect to time • DC Sweep – View the response to a range of DC inputs • AC Sweep – View the response to a range of frequencies

Run the Simulation

• Press the blue arrow in the toolbar on the top.

Select Output

Output 1

More Output

Output 2

A More Complicated Example • Input – 5Vpeak, 2kHz Sine Wave pulsed for 5ms ever 20ms starting 1ms and an output impedence of 1kOhm • The input passes through a simple BPF with a gain of 1.

• The output of the BPF is rectified and passed through an RC filter with a time constant of 0.5ms.

• Put the output across a 1Meg Ohm resistor.

Using Heirarchy

•You can break your Pspice design into modules.

•These modules can be linked together at the top level.

VDC VSI N

Signal Source

MULT – From ABM VPULS E

Input Port Band Pass Filter LM741 from OPAMP Output Port Notice the power supply connections

Rectifier

Top Level

Simulation • Is the output what you expect?

Simulation

Perform Your Own Simulations This presentation was adapted from a presentation by Farid Hassani